Position oven rack in the center of the oven; preheat oven to 375F; line a large baking sheet with parchment paper; set aside.,In a bowl, mix both flours, baking powder, and salt together.,Cut in the butter with a pastry cutter, pressing the flour and butter together through the tines until the mixture resembles coarse meal.,Stir in the walnut pieces, whole egg, yogurt, and 1/4 cup maple syrup; stir just until a batter comes together into a moist dough.,______,Knead a few times, just until the dough begins to hold its shape.,If it is sticky, add a touch more cake flour, just to keep it moist but stable.,Gently press-do not rollinto a circle about 8 inches in diameter.,Slice the circle into 8 wedges, like a pie.,Transfer these to the prepared baking sheet.,Whisk the egg yolk, remaining 1 teaspoon maple syrup, and milk in a small bowl.,Brush the mixture over the scones.,Bake about 20 minutes, until brown and firm.,Cool on a baking sheet for a couple of minutes, then transfer to a wire rack to continue cooling for at least 10 minutes before serving.